1. Field of the Invention
The present invention relates to a gas turbine combustor and a method for operating the same.
2. Description of the Related Art
As the regulations and social needs relating to environmental protection are being increasingly tightened nowadays, gas turbines are also required to be even more highly efficient and to achieve low NOx emissions.
One effective way to enhance the efficiency of a gas turbine is to raise the gas temperature at the entrance of the turbine. In this case, however, an increase in NOx emission level is liable to result from an increase in internal flame temperature of the gas turbine combustor.
There exist gas turbine combustors that employ a premixed combustion scheme in which a premixture of fuel and air is supplied to and burned in the gas turbine combustor for reduced NOx emissions.
Such a gas turbine combustor that employs premixed combustion includes a premixer and a combustion chamber. The premixer is a constituent element of a burner and premises fuel and air. The combustion chamber is positioned downstream of the premixer to burn the premixed fuel and air.
Premixed combustion creates a uniform flame temperature and thus is effective for seducing NOx emissions. An increase in flame temperature, however, increases the likelihood of flashback, an event that the flame unexpectedly flows back from the combustion chamber of the gas turbine combustor to the premixer which forms part of the burner positioned, upstream of the combustion chamber. For this reason, there is a growing need for a gas turbine combustor having a capability to suppress NOx emissions and an anti-flashback property.
Japanese Patent No. 3960166 discloses a technique concerning a gas turbine combustor having an NOx emissions suppression capability and an anti-flashback property. In the gas turbine combustor pertaining to the technique described in Japanese Patent No. 3960166, a plurality of fueling nozzles and a plurality of air injection holes are coaxially arranged and a plurality of coaxial jet flows of fuel and air are supplied to a combustion chamber and burned therein.
Compared with a conventional gas turbine combustor based on prefixed combustion, the gas turbine combustor, disclosed in Japanese Patent No. 3960166, that supplies the plurality of coaxial jet flows of fuel and air to the combustion chamber and burns the coaxial jet flows therein, can rapidly mix the fuel and the air at a very short distance and in this context, has both an NOx emissions suppression, capability and an anti-flashback property. In addition, since the conventional gas turbine combustor of interest has high anti-flashback performance, the gas turbine combustor is also applicable to fuels high in combustion rate as well as in hydrogen content, such as the coal gasification product gases and coke oven gases adopted in conventional diffuse combustion schemes.
Japanese Patent No. 3960166 also discloses a structure in which fueling nozzles and air injection holes are arranged in a plurality of rows concentrically from the burner center so as to form the plurality of coaxial jet flows of fuel and air.
In a gas turbine with a plurality of combustors, on the other hand, a sparking plug is mounted on two combustor cans present at diagonal positions, for example, and when the gas turbine combustors are ignited, the sparking plugs are fired to cause spark ignition of the combustors. The adjacent combustors are connected to each other via tubes called cross fixe tubes, through which combustion gases from the ignited combustors propagate through the cross fire tubes to the adjacent combustors, thereby igniting all combustors. In this way, the plurality of combustors can be ignited efficiently. JP-2009-52795-A discloses a multi-burner structure including a plurality of burners that form one combustor, in the multi-burner structure of which, a phase in gap between the burners is matched to a phase of cross fire tubes in order to efficiently supply combustion gases to the cross fire tubes during ignition.